Power steering valve

A power steering valve comprising:

• a housing including a supply flow path into which hydraulic fluid flows from a hydraulic pressure source, a tank flow path from which the hydraulic fluid flows out to a reservoir tank, and a plurality of control flow paths from which the hydraulic fluid flows out to a steering cylinder and into which the hydraulic fluid flows from the steering cylinder;
• a sleeve cylindrically shaped, having a circumferential wall in which a plurality of openings into which the hydraulic fluid flows and from which the hydraulic fluid flows out is formed in a penetrating manner, and held in such a way as to be able to rotate in a circumferential direction within the housing;
• a spool cylindrically shaped, having a circumferential surface in which a plurality of axial grooves into and through which the hydraulic fluid from a predetermined one of the openings of the sleeve flows is drilled, held in such a way as to be able to rotate within a predetermined range in a circumferential direction within the sleeve, and having a second end portion to which an input shaft of a steering wheel is coupled;
• a gerotor fixed to a first end portion of the housing and configured to be driven by the hydraulic fluid which flows out from a predetermined one of the openings of the sleeve;
• and
• a drive shaft having a first end portion which meshes with an inner rotor of the gerotor and a second end portion which is pivotally supported in a swingable manner by the sleeve with use of a pin,
• wherein the hydraulic fluid which flows in from the gerotor is configured to flow through according to an amount of overlap between a predetermined one of the axial grooves of the spool and a predetermined one of the openings of the sleeve, which is set in association with rotation of the steering wheel, and flow out to the steering cylinder via the control flow paths,
• wherein the drive shaft is formed with a dimension defined in such a manner that an overall length thereof Ld is in a range of:
• (¼)·Ls≤Ld≤(½)·Ls
• relative to an overall length Ls of the sleeve, and
• wherein the pin is arranged at a position nearer the gerotor in an axial direction than a middle position in the sleeve;
• wherein the housing includes a pressure adjusting unit which adjusts an inflow pressure of the hydraulic fluid which flows from the supply flow path into the sleeve, and an LS flow path which communicates with the pressure adjusting unit, and has a circuit configuration not to communicate with the supply flow path via the sleeve and the spool when the steering wheel is not rotationally operated, and has a circuit configuration to communicate with the supply flow path via the sleeve and the spool when the steering wheel is rotationally operated,
• wherein the sleeve includes, on an outer circumferential surface of a first end portion thereof, an LS portion which causes a part of the hydraulic fluid flowing in from the gerotor to flow out to the LS flow path, and
• wherein the pin is arranged at a position between a position at which an opening which communicates with the supply flow path out of the openings is arranged and a position at which the LS portion is arranged in the sleeve.